Various types of equipment, instruments, etc., used in hospitals, laboratories, and the like are sterilized for disinfection and for killing bacteria and fungi. Plasma treatment is known as a sterilization treatment (see, for example, “3.3.1 Teiatsuryoku hoden purazuma wo mochiita mekkin jikken [3.3.1 Sterilization Experiment Using Low-pressure Discharge Plasma]” in Non-patent Literature 1).
Plasma treatment is used not only for sterilization treatment but also for plasma dry etching and plasma cleaning of the surface of items to be treated, such as electronic parts, in the process of producing semiconductor devices.
Plasma dry etching generally comprises applying high-frequency power to electrodes disposed in a reaction chamber that is a vacuum vessel, plasmarizing a gas for generating plasma introduced in the reaction chamber, and etching a semiconductor wafer with high precision. Plasma cleaning removes metal oxides, organic substances, burrs, etc., deposited on or adhering to the surface of items to be treated, such as electronic parts, to improve bonding or the wettability of solder, thus enhancing bonding strength and improving adhesion to a sealing resin and wettability.
A known method for detecting the completion of such plasma treatment is a method using a plasma treatment detection indicator in which a color-changing layer changes color in a plasma treatment atmosphere.
For example, Patent Literature 1 discloses an ink composition for detecting plasma treatment, the composition comprising 1) at least one member selected from the group consisting of anthraquinone colorants, azo colorants, and phthalocyanine colorants and 2) at least one member selected from the group consisting of binder resins, cationic surfactants, and extenders, a gas for generating plasma used for the plasma treatment containing at least one member selected from the group consisting of oxygen and nitrogen; and a plasma treatment detection indicator comprising a color-changing layer formed on a base material, the color-changing layer comprising the ink composition.
Patent Literature 2 discloses an ink composition for detecting inert gas plasma treatment, the composition comprising 1) at least one member selected from the group consisting of anthraquinone colorants, azo colorants, and methine colorants and 2) at least one member selected from the group consisting of binder resins, cationic surfactants, and extenders, the inert gas containing at least one member selected from the group consisting of helium, neon, argon, krypton, and xenon; and a plasma treatment detection indicator comprising a color-changing layer formed on a base material, the color-changing layer comprising the ink composition.
These plasma treatment detection indicators are useful indicators that allow the completion of plasma treatment to be determined by a change in the color of the color-changing layer. To enable the color change behavior of the color-changing layer to be determined with further certainty, a fibrous base material or a synthetic resin base material comprising a coloring pigment (hiding pigment) such as titanium dioxide, both of which are capable of hiding the color of the place on which they are disposed, is generally used as a base material.
However, when a fibrous base material or a synthetic resin base material comprising a coloring pigment is used, the surface of the base material may be affected by plasma in plasma treatment, causing fine fiber pieces or coloring pigment to be generated in a powder form. When such fine fiber pieces or coloring pigment is adhered to the color-changing layer, it may affect the accurate determination of a color change in the color-changing layer after plasma treatment.
Accordingly, development has been desired for a plasma treatment detection indicator that uses a fibrous base material or a synthetic resin base material comprising a coloring pigment as a base material and in which fine fiber pieces or coloring pigment is prevented from being generated in a powder form from the base material in plasma treatment.